Preschoolers exposed to nighttime light lack melatonin

One hour lowers sleep-promoting hormone 88 percent

March 5, 2018

Science Daily/University of Colorado at Boulder

A new study found that preschoolers exposed to bright light at bedtime had an 88 percent reduction in melatonin levels. Anatomical differences in their young eyes may make them more vulnerable to adverse impacts of bright light, the researchers say.

Exposing preschoolers to an hour of bright light before bedtime almost completely shuts down their production of the sleep-promoting hormone melatonin and keeps it suppressed for at least 50 minutes after lights out, according to new University of Colorado Boulder research.

The study, published today in the journal Physiological Reports, is the first to assess the hormonal impact nighttime light exposure can have on young children.

The study comes at a time when use of electronics is rapidly expanding among this age group and adds to a growing body of evidence suggesting that-because of structural differences in their eyes-children may be more vulnerable to the impact light has on sleep and the body clock.

"Although the effects of light are well studied in adults, virtually nothing is known about how evening light exposure affects the physiology, health and development of preschool-aged children," said lead author Lameese Akacem, a CU Boulder instructor and researcher in the Sleep and Development Lab. "In this study we found that these kids were extremely sensitive to light."

For the study, the researchers enrolled 10 healthy children ages 3 to 5 years in a seven-day protocol. On days one through five, the children followed a strict bedtime schedule to normalize their body clocks and settle into a pattern in which their melatonin levels began to go up at about the same time each evening.

On day six, Akacem's team came into the children's homes and created a dim-light environment, covering windows with black plastic and swapping out existing lights with low-wattage bulbs. This ensured that all the children were exposed to the same amount of light-which can influence melatonin timing and levels-before samples were taken.

That afternoon, the researchers took periodic saliva samples to assess melatonin levels at various times. The following evening, after spending the day in what they playfully referred to as "the cave," the children were invited to color or play with magnetic tiles on top of a light table emitting 1,000 lux of light (about the brightness of a bright room) for one hour.

Then the researchers took samples again, comparing them to those taken the night before.

Melatonin levels were 88 percent lower after bright light exposure. Levels remained suppressed at least 50 minutes after the light was shut off.

Direct comparisons between this study and studies in adults must be made with caution because of differing research protocols, the researchers stress. However, they note that in one study, a one-hour light stimulus of 10,000 lux (10 times that of the current study) suppressed melatonin by only 39 percent in adults.

"Light is our brain clock's primary timekeeper," explains senior author Monique LeBourgeois, an associate professor in the Department of Integrative Physiology. "We know younger individuals have larger pupils, and their lenses are more transparent. This heightened sensitivity to light may make them even more susceptible to dysregulation of sleep and the circadian clock."

She explains that when light hits the retina in the eye in the evening, it produces a cascade of signals to the circadian system to suppress melatonin and push back the body's entrance into its "biological night." For preschoolers, this may not only lead to trouble falling asleep one night, but to chronic problems feeling sleepy at bedtime.

Melatonin also plays a role in other bodily processes, regulating temperature, blood pressure and glucose metabolism.

"The effects of light at night exposure can definitely go beyond sleep," Akacem said.

The study sample size was small and it used only one intensity of light, 1,000 lux, which is far greater than the intensity of a typical handheld electronic device, she notes.

With a new $2.4 million grant from the National Institutes of Health, LeBourgeois recently launched a study in which she will expose 90 children to light of different intensities to determine how much it takes to impact the circadian clock.

"The preschool years are a very sensitive time of development during which use of digital media is growing more and more pervasive," Le Bourgeois said. Use of electronic media among young children has tripled since 2011. "We hope this research can help parents and clinicians make informed decisions on children's light exposure."

The takeaway for parents today: Dim the lights in the hours before bedtime.

https://www.sciencedaily.com/releases/2018/03/180305160151.htm

Effects of night-time light on internal body clock

April 30, 2018

Science Daily/The Physiological Society

New research published in The Journal of Physiology has illuminated the effects of night-time light exposure on internal body clock processes. This is important for helping those who have poor quality sleep, such as shift workers, and could help improve treatments for depression.

The body has an internal clock that causes various physiological processes to oscillate in 24-h cycles, called circadian rhythms, which includes daily changes in sleepiness. Light is the strongest environmental time cue that resets the body's internal 24-h clock. Melatonin is a hormone produced in the brain at night that regulates this body clock and exposure to light before bedtime may reduce sleep quality by suppressing its production. The research team aimed to explore the link between the physiological process that enables our internal body clock to synchronise to external time cues (i.e. day and night) -- called circadian phase resetting -- and suppression of melatonin.

Melatonin suppression and circadian phase resetting are often correlated such that high levels of melatonin suppression can be associated with large shifts of the body clock. This association between the two responses has often been assumed to represent a functional relationship, resulting in the acceptance that one could be used as a proxy measure for the other. Circadian phase resetting is more difficult to measure than melatonin suppression, meaning the latter has often been used to assess disruption to the body clock caused by light exposure at night. However, this research has found that the magnitude of the shift in internal body clock is functionally independent from melatonin suppression. This casts doubt on the use of melatonin suppression as a proxy for circadian phase resetting. This knowledge may shape future research designed to improve treatments for depression and shift work sleep disorder.

The researchers tested the association between melatonin suppression and circadian phase resetting in participants who received either continuous or intermittent bright light exposure at night. This research procedure involved each participant completing a 9-10 day inpatient study at Brigham and Women's Hospital, Boston, under highly controlled laboratory conditions with strict control over their sleep/wake, activity and light/dark schedules. Intermittent exposure patterns were found to show significant phase shifts with disproportionately less melatonin suppression. Moreover, each and every intermittent bright light pulse induced a similar degree of melatonin suppression, but did not appear to cause an equal magnitude of phase shift.

Despite the results of this study suggesting functional independence in circadian phase resetting and melatonin suppression responses to exposure to light at night, the study's conclusions may be restricted by the limited sample size in each light exposure condition.

Lead author Dr Shadab Rahman is excited by his team's findings, and is looking forward to investigating new avenues of interest they have opened up:

"Overall, our data suggest that melatonin suppression and phase resetting are sometimes correlated, but ultimately are regulated by separate neurophysiological processes. Therefore melatonin suppression is not a reliable surrogate for phase resetting. This is an important consideration for developing light-therapy treatments for people who have poor quality sleep and biological clock disruption, such as shift workers, or disorders such as depression. Additional work is needed to optimize light therapy protocols used as treatment."

https://www.sciencedaily.com/releases/2018/04/180430075635.htm

One in three older adults take something to help them sleep but many don't talk to their doctors

1 in 12 people over age 65 take prescription sleep medications, which carry health risks for older people

September 27, 2017

Science Daily/Michigan Medicine - University of Michigan

Sleep doesn't come easily for nearly half of older Americans, and more than a third have resorted to some sort of medication to help them doze off at night, a new national poll finds. But most said they hadn't talked to their doctor about their sleep, even though more than a third said their sleep posed a problem. Half believe -- incorrectly -- that sleep problems just come naturally with age.

But most poll respondents said they hadn't talked to their doctor about their sleep, even though more than a third said their sleep posed a problem. Half believe -- incorrectly -- that sleep problems just come naturally with age.

The poll was conducted by the University of Michigan Institute for Healthcare Policy and Innovation, and is sponsored by AARP and Michigan Medicine, U-M's academic medical center.

Those who turn to medications may not realize that prescription, over-the-counter and even "natural" sleep aids carry health risks, especially for older adults, either alone or in combination with other substances. In fact, national guidelines strongly warn against prescription sleep medicine use by people over age 65.

Despite this, the nationally representative poll of people ages 65 to 80 finds that 8 percent of older people take prescription sleep medicine regularly or occasionally. Among those who report sleep troubles three or more nights a week, 23 percent use a prescription sleep aid. Most who use such drugs to help them sleep had been taking them for years. Manufacturers and the U.S. Food and Drug Administration say such drugs are only for short-term use.

Medication: not the only option

"Although sleep problems can happen at any age and for many reasons, they can't be cured by taking a pill, either prescription, over-the-counter or herbal, no matter what the ads on TV say," says poll director Preeti Malani, M.D., a U-M physician trained in geriatric medicine. "Some of these medications can create big concerns for older adults, from falls and memory issues to confusion and constipation," even if they're sold without a prescription.

"The first step for anyone having trouble sleeping on a regular basis should be to talk to a doctor about it," she continues. "Our poll shows that nearly two-thirds of those who did so got helpful advice -- but a large percentage of those with sleep problems simply weren't talking about it."

She notes that non-medication-based sleep habits are the first choice for improving sleep in older people. Sleep and health

In all, 46 percent of those polled had trouble falling asleep one or more nights a week. Fifteen percent of the poll respondents said they had trouble falling asleep three or more nights a week.

Other health conditions can contribute to sleep difficulties. Twenty-three percent of poll respondents who had trouble sleeping said it was because of pain. And 40 percent of those with frequent sleep problems said their overall health was fair or poor. Other reasons for sleep troubles included having to get up to use the bathroom at night, and worry or stress.

Insomnia and other irregular sleep patterns can interfere with daytime functioning, and are associated with memory issues, depression and an increased risk of falls and accidents. Even so, many said they didn't see sleep issues as a health problem -- in fact, this belief was the most common reason that poll respondents said they didn't talk to their doctor about sleep.

This also highlights the need for doctors to ask their older patients about their sleep habits and what they're doing to address any issues they may be having

"We know that sleep is a critical factor for overall health as we age, and this new research highlights sleep problems as both a significant health issue for older adults and an underacknowledged one both by patients and their providers," says Alison Bryant, Ph.D., senior vice president of research for AARP. "We need to help people understand that lack of sleep is not just a natural part of aging."

More about medication use

In all, 14 percent of the poll respondents said they regularly took a prescription sleep medication, prescription pain medication, OTC sleep aid or herbal supplement to help them sleep. Another 23 percent took one of these options occasionally; most of the occasional users said they chose OTC sleep aids.

The most recent Beers Criteria established by the American Geriatrics Society, which guides the use of medications among older people, gives a strong warning against use of prescription sleep drugs, which are sold under such names as Ambien, Lunesta and Sonata.

Meanwhile, even though OTC sleep aids can be purchased without a doctor's guidance or prescription, they still carry health risks for older people, Malani notes. Most of them contain diphenhydramine, an antihistamine that can cause side effects such as confusion, urinary retention and constipation.

Among poll respondents with frequent sleep problems who took something occasionally to help them sleep, OTC sleep remedies were the most common choice. But among those with frequent sleep issues who took something on a regular basis to try to sleep, prescription sleep medications were the most common option, with 17 percent reporting use.

Use of melatonin and other herbal remedies may be perceived as safer, but less is known about their potential side effects and they are not subject to the FDA's approval process for medications, says Malani. But any issue that prompts someone to buy an OTC or herbal remedy on a regular basis is something they should discuss with their doctor, she adds.

The poll results are based on answers from a nationally representative sample of 1,065 people ages 65 to 80, who answered a wide range of questions online. Questions were written, and data interpreted and compiled, by the IHPI team. Laptops and Internet access were provided to poll respondents who did not already have it.

https://www.sciencedaily.com/releases/2017/09/170927093322.htm

Short winter days trigger aggression hormones differently based on sex

Territorial hamsters reveal biological mechanism behind the difference in male versus female aggression

November 18, 2015

Science Daily/Indiana University

Researchers have discovered a hormonal mechanism in hamsters that connects short winter days with increased aggression in females, and that it differs from the mechanism that controls this same response in males.

https://images.sciencedaily.com/2015/11/151118070754_1_540x360.jpg

A female hamster displays aggressive behavior.

Credit: Frank Scherbarth

The work, which advances basic knowledge on the connection between certain sex hormones and aggression, could go on to advance research on the treatment of inappropriate aggression in humans.

The study appears online Nov. 18 in the Proceedings of the Royal Academy B. The research is a collaboration between the IU Bloomington College of Arts and Sciences' Department of Biology and Department of Psychological and Brain Sciences.

"This study reveals a ripe area for research," said Nikki Rendon, a Ph.D. student in biology and lead author on the study.

"The results show for the first time that melatonin acts directly on the adrenal glands in females to trigger a 'seasonal aggression switch' from hormones in the gonads to hormones in the adrenal glands -- a major contrast to how this mechanism works in males."

Other IU authors were Gregory Demas, professor of biology, and Dale Sengelaub, professor of psychological and brain sciences.

Rendon is a member in the lab of Demas, who was part of the team that first discovered a connection between shorter days and aggression in animals.

Demas' earlier research also found that wintertime aggression in hamsters arises not from sex hormones in the gonads -- ovaries in females and testes in males, which grow less active during shorter days -- but rather the adrenal glands, located at the top of the kidneys.

Melatonin is a hormone that rises in the body during darkness and lowers during daylight. The hormone from the adrenal gland is dehydroepiandrosterone, or DHEA, a sex steroid shown to affect aggression levels in mammals and birds, and possibly humans. Professional sports competitions have banned the use of DHEA in athletes.

In another previous study, Demas' lab found that melatonin -- in concert with a hormone secreted by the brain's pituitary gland called adrenocorticotropic, or ACTH -- increases the output and enhances the effects of DHEA from adrenal glands in males.

In contrast, Rendon and colleagues' new study reveals that melatonin acts directly on the adrenal glands in females to trigger the release of DHEA, without the need for the pituitary hormone.

DHEA can be converted to androgens and estrogens, which affect aggression in both males and females. In females, DHEA appears to compensate for low levels of estradiol -- a form of estrogen -- that occurs during the winter.

Evolutionarily, wintertime aggression may confer an advantage during periods of scarce food.

"This study, which builds upon our previous work investigating the connection between short days and aggression in males, shows noteworthy hormonal mechanisms in females and provides important new insights into the role of sex in these mechanisms," Demas said.

The research was conducted in Siberian hamsters, or Phodopus sungorus, a species with a similar adrenal system to humans. About 130 hamsters were exposed to long days for a week, after which 45 were exposed to shorter days for 10 weeks. A random subset also received an injection of ACTH.

A highly territorial species, the hamsters were then placed in situations where one hamster was perceived as an intruder into the other's territory, sparking aggressive actions and short physical fights. The scientists then tracked certain actions, such as the time until an attack, the number of attacks and the length of the attacks, to assign an "aggression score."

The female hamsters exposed to shorter days had increased levels of both melatonin and DHEA -- and higher aggression scores -- along with physical changes in their adrenal glands.

Females exposed to longer days did not experience these changes, including those that had received an injection of ACTH, which is known to trigger the release of DHEA.

Collectively, the results show that melatonin is the primary regulator of aggression in females.

"It's growing increasingly clear that sex hormones play an important role in controlling aggression in both males and females -- but females, human and non-human, are traditionally vastly understudied in the sciences," Rendon said. "By conducting this research on females, we are increasing our understanding of hormones and social behavior in a field currently dominated by discussions on testosterone regulating aggression in males."

http://www.sciencedaily.com/releases/2015/11/151118070754.htm

Blue light emitted by screens damages our sleep

August 22, 2017

Science Daily/University of Haifa

The short-wavelength blue light, emitted by the screens we watch, damages the duration, and even more so, the quality of our sleep. The study also found that watching screens that emit red light does not cause damage, and sleep after exposure to it was similar to normal sleep.

Previous studies have already shown that watching screens before going to sleep damages our sleep. It has also been found that exposure to blue light with wave lengths of 450-500 nanometers suppresses the production of melatonin, a hormone secreted at night that is connected with normal body cycles and sleep. The new study, published in the journal Chronobiology International, was undertaken by researchers Prof. Abraham Haim, head of the Israeli center for interdisciplinary research in chronobiology at the University of Haifa; doctorate student Amit Shai Green of the Center for Interdisciplinary Chronobiological Research at the University of Haifa and the Sleep and Fatigue Center at Assuta Medical Center; Dr. Merav Cohen-Zion of the School of Behavioral Sciences at the Academic College of Tel Aviv-Yafo; and Prof. Yaron Dagan of the Research Institute for Applied Chronobiology at Tel Hai Academic College. The researchers sought to examine whether there is any difference in sleep patterns following exposure to blue screen light as compared to red light prior to sleep, and furthermore, to find which is more disruptive: wavelength or intensity?

The study participants were 19 healthy subjects aged 20-29 who were not aware of the purpose of the study. In the first part of the trial, the participants wore an actigraph for one week (an actigraph is a device that provides an objective measurement of the time when an individual falls asleep and wakes up). They also completed a sleep diary and a questionnaire about their sleeping habits and quality of sleep. In the second part of the trial, which took place at Assuta's Sleep Laboratory, the participants were exposed to computer screens from 9 p.m. to 11 p.m. -- the hours when the pineal gland begins to produce and excrete melatonin. The participants were exposed to four types of light: high-intensity blue light, low-intensity blue light, high-intensity red light, and low-intensity red light. Following exposure to light, they were connected to instruments that measure brain waves and can determine the stages of sleep a person undergoes during the course of the night, including awakenings not noticed by the participants themselves. In the morning, the participants completed various questionnaires relating to their feelings.

On average, exposure to blue light reduced the duration of sleep by approximately 16 minutes. In addition, exposure to blue light significantly reduced the production of melatonin, whereas exposure to red light showed a very similar level of melatonin production to the normal situation. The researchers explain that the impaired production of melatonin reflects substantial disruption of the natural mechanisms and the body's biological clock. Thus, for example, it was found that exposure to blue light prevents the body from activating the natural mechanism that reduces body temperature. "Naturally, when the body moves into sleep it begins to reduce its temperature, reaching the lowest point at around 4:00 a.m. When the body returns to its normal temperature, we wake up," Prof. Haim explains. "After exposure to red light, the body continued to behave naturally, but exposure to blue light led the body to maintain its normal temperature throughout the night -- further evidence of damage to our natural biological clock."

The most significant finding in terms of the disruption of sleep was that exposure to blue light drastically disrupts the continuity of sleep. Whereas after exposure to red light (at both intensities) people woke up an average of 4.5 times (unnoticed awakenings), following exposure to weak blue light 6.7 awakenings were recorded, rising to as many as 7.6 awakenings following exposure to strong blue light. Accordingly, it is hardly surprising that the participants reported in the questionnaires that the felt more tired and in a worse mood after exposure to blue light.

"Exposure to screens during the day in general, and at night in particular, is an integral part of our technologically advanced world and will only become more intense in the future. However, our study shows that it is not the screens themselves that damage our biological clock, and therefore our sleep, but the short-wave blue light that they emit. Fortunately various applications are available that filter the problematic blue light on the spectrum and replace it with weak red light, thereby reducing the damage to the suppression of melatonin," concludes Prof. Haim.

https://www.sciencedaily.com/releases/2017/08/170822103434.htm

Artificial light from digital devices lessens sleep quality

Melatonin skyrockets when blue light is blocked

July 28, 2017

Science Daily/University of Houston

Blue light emitted from digital devices could contribute to the high prevalence of reported sleep dysfunction, suggests new research.

There's no doubt we love our digital devices at all hours, including after the sun goes down. Who hasn't snuggled up with a smart phone, tablet or watched their flat screen TV from the comfort of bed? A new study by researchers at the University of Houston College of Optometry, published in Ophthalmic & Physiological Optics, found that blue light emitted from those devices could contribute to the high prevalence of reported sleep dysfunction.

Study participants, ages 17-42, wore short wavelength-blocking glasses three hours before bedtime for two weeks, while still performing their nightly digital routine. Results showed about a 58 percent increase in their nighttime melatonin levels, the chemical that signals your body that it's time to sleep. Those levels are even higher than increases from over-the-counter melatonin supplements, according to Dr. Lisa Ostrin, the UH College of Optometry assistant professor who lead the study.

"The most important takeaway is that blue light at night time really does decrease sleep quality. Sleep is very important for the regeneration of many functions in our body," Ostrin said.

Wearing activity and sleep monitors 24 hours a day, the 22 study participants also reported sleeping better, falling asleep faster, and even increased their sleep duration by 24 minutes a night, according to Ostrin.

The largest source of blue light is sunlight, but it's also found in most LED-based devices. Blue light boosts alertness and regulates our internal body clock, or circadian rhythm, that tells our bodies when to sleep. This artificial light activates photoreceptors called intrinsically photosensitive retinal ganglion cells (ipRGCs), which suppresses melatonin.

Ostrin recommends limiting screen time, applying screen filters, wearing computer glasses that block blue light, or use anti-reflective lenses to offset the effects of artificial light at nighttime. Some devices even include night mode settings that limit blue light exposure.

"By using blue blocking glasses we are decreasing input to the photoreceptors, so we can improve sleep and still continue to use our devices. That's nice, because we can still be productive at night," Ostrin said.

According to the most recent findings from the National Sleep Foundation's Sleep Health Index®, while three quarters of Americans are satisfied with their sleep over the past week, more than four in ten Americans reported that their daily activities were significantly impacted by poor or insufficient sleep at least once during the past seven days.

https://www.sciencedaily.com/releases/2017/07/170728121414.htm

Exposure to early evening sunlight in spring creates teenage night owls

July 26, 2010

Science Daily/Rensselaer Polytechnic Institute

In the spring, later sunset and extended daylight exposure delay bedtimes in teenagers, according to new research.

"Biologically, this increased exposure to early evening light in the spring delays the onset of nocturnal melatonin, a hormone that indicates to the body when it's nighttime," explains Mariana Figueiro, Ph.D., associate professor. "This extended exposure adds to the difficulties teens have falling asleep at a reasonable hour."

Over time when coupled with having to rise early for school, this delay in sleep onset may lead to teen sleep deprivation and mood changes, and increase risk of obesity and perhaps under-performance in school, according to Figueiro.

"This is a double-barreled problem for teenagers and their parents," says Figueiro. "In addition to the exposure to more evening daylight, many teens also contend with not getting enough morning light to stimulate the body's biological system, also delaying teens' bedtimes."

Measuring "Circadian Light"

In the study, the Algonquin Middle School students were exposed to significantly more "circadian light" in the early evening during spring than in winter, resulting in both delayed melatonin onset and shorter self-reported sleep durations. Each subject wore a Daysimeter, a small, head-mounted device developed by the LRC to measure an individual's exposure to daily "circadian light," as well as rest and activity patterns. The definition of circadian light is based upon the potential for light to suppress melatonin synthesis at night, as opposed to measuring light in terms of how it stimulates the visual system.

This study, sponsored by the U.S. Green Building Council (USGBC) and, in part, by a grant from a Trans-National Institutes of Health Genes, Environment and Health Initiative (NIH-GEI), is the first to relate field measurements of circadian light exposures to a well-established circadian marker (the rise in evening melatonin levels) during two seasons of the year.

In a previous field study, also funded by USGBC and NIH-GEI and published in Neuroendocrinology Letters, Figueiro and Rea examined the impact of morning light on teen sleep habits and found that removing short-wavelength (blue) morning light resulted in a 30-minute delay in sleep onset by the end of a five-day period.

http://www.sciencedaily.com/releases/2010/07/100726124420.htm

Blue-Blocking Glasses to Improve Sleep and ADHD Symptoms Developed

November 14, 2007

Science Daily/John Carroll University

Scientists at John Carroll University, working in its Lighting Innovations Institute, have developed an affordable accessory that appears to reduce the symptoms of ADHD. Their discovery also has also been shown to improve sleep patterns among people who have difficulty falling asleep. The John Carroll researchers have created glasses designed to block blue light, therefore altering a person's circadian rhythm, which leads to improvement in ADHD symptoms and sleep disorders.

The individual puts on the glasses a couple of hours ahead of bedtime, advancing the circadian rhythm. The special glasses block the blue rays that cause a delay in the start of the flow of melatonin, the sleep hormone. Normally, melatonin flow doesn't begin until after the individual goes into darkness. Studies indicate that promoting the earlier release of melatonin results in a marked decline of ADHD symptoms.

http://www.sciencedaily.com/releases/2007/11/071112143308.htm